Abstract: In order to explore the effects of chlorpyrifos on earthworms, the acute toxicity of chlorpyrifos to Eisenia foetida and the effects of chlorpyrifos on the growth and reproduction of earthworms were investigated by exposing E.foetida to chlorpyrifos in artificial soil. The results indicated that the 14 d-LC50 value of chlorpyrifos to E.foetida was 88.75 mg a.i./kg dry soil; After exposure to chlorpyrifos at 10, 25, 50, 80 and 100 mg a.i./kg dry soil for 28 d, the weight of E.foetida reduced significantly except the treatment of 10 mg a.i./kg dry soil; the body weight reducing rates were 9.8%, 15.7%, 17.5%, 23.9% and 27.0%, respectively, demonstrating a high correlation between the body weight reducing rate and the concentration(Pr=0.984). The reproduction inhibition rates of chlorpyrifos E.foetida at 10, 25, 50, 80 and 100 mg/kg dry soil were 32.26%, 80.97%, 89.03%, 89.68% and 97.42%, respectively, indicating a certain correlation(P >0.01, r=0.788) between the reproduction inhibition rate and the concentration. The 28 d-lowest observed effect concentration(LOEC) value of chlorpyrifos to the growth and reproduction of E.foetida was 25 mg/kg dry soil.